Fly Strike : Illnesses, Injuries and Parasites

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So I apologize in advance because this will be a little bit long winded due to me being compulsively long winded. Unfortunately I have become a little too familiar with fly strike this past year. I am not including any photos because it really is a horror to see and it is impossible to not recognize on sight.

So I've had 4 strikes occur on two German Angora does. Three strikes on one doe, and one on her daughter. My original herd suffered from genetic urine sludge which I won't get into here. End result being a dozen rabbits with wet urine soaked bottoms which smelled powerfully of rank abnormal smelling urine. That came and went as I did my very best to keep them trimmed enough to keep most of it off of them. I was not terribly successful with that. Regardless of being prime targets for two and a half years with uncontrolled sludge none of them ever attracted any flies. Eventually after trying countless nutritional changes and supplements with poor or no results I was able to get it fully controlled, by accident, with a high fat feed. Purina Show of all things.

Strike one

Not long after all the sludge rabbits, and I had 5 left by then, were nice and dry and no longer producing sludge I had my first fly strike. This was Sept of last year. It occurred on a doe who was just under 3 years of age. So it took several revolting hours to get her sheared down, picked and flushed free of maggots and she fully recovered. She was just a little bit off from time to time after this strike. It was very subtle, came and went, she never went off her feed, never showed any pain postures or behavior, just every now and then she just wasn't quite herself.

Strike two and three

So fast forward to this June. I found some leftover feed in the bowl of the above doe's daughter. I pulled her out looked her over and she had a fly strike. Again, sheared the surrounding area because I recalled how they tried to escape into the wool and hide from last time, picked and flushed until I couldn't find anymore maggots. Then went in, did some hunting on the internet and came across a fly strike spray for sheep. So I made my own with Ivermectin and water, went back out and sprayed that doe's fly strike area thoroughly. I did not find anymore maggots on her the next day so whew.

That same day that Mini proved to be 100% maggot free, her mom, the first doe, had food left in her bowl and that doe never left a scrap ever. Pulled her out, and yep fly strike also, her second one. I had an even bigger problem with this doe though as I was picking and flushing and cursing my life I could see that there were hundreds and hundreds of maggots too small for me to pick manually. So I panicked, grabbed that ivermectim spray and soaked the maggot ridden area. I checked her 4 hours later and all the maggots were dead and most had also fallen off. They had not managed to do much more damage to her after I sprayed them. So I cleaned her up, and she recovered again but healed a bit slower than her daughter. I went over every rabbit in that barn with a fine toothed comb. I sheared all butts and 3 inches above their tails so I could clearly see that area and was on full alert for any more but that was the extent of it. No more strikes.

Strike 4

Aug 18th I found my older doe covered in blood. I could see it soaking the inside of one hind leg and foot. I thought it was maybe an injury, pulled her out but no it was again fly strike, her third, but this time with profuse bleeding. Again on a perfectly clean and dry animal. None are housed with pans, they are all single stack above dry clear ground which I muck out regularly. They have fans for ventilation, there is no detectable odors in there, and I never see any flies. There was no reason for this rabbit to be struck so many times while every other rabbit was ignored, except her daughter.

I trimmed a little to expose the maggots sprayed her down with ivermectin spray. I already knew I was going to euthanize her but I could not do it that very moment and I also couldn't stand to let those things chew on her one moment longer. I euthanized her an hour and a half later, she was one of those, you know, the special ones, the ones that break your heart, but I necropsied her anyway. I found her absolutely riddled with cancer. Uterine cancer that had metastasized to her lungs. A mass on her bladder, lungs so full of masses that they were hard, her heart was rock hard on one side, soft on the other...She was basically the walking dead and I really do hate how rabbits hide things so successfully. I did not expect that from a rabbit whose only unusual behavior was acting a little hot for a few hours when no one else was, and a slightly abnormal gait.

So I am thinking that they are being attracted by the smell of cancer. Dogs can smell it. nurses can smell it, I've even smelled it way back when I was a nurse's aid. That leaves me very concerned about Mini who is the same age as her mom was when first strike happened, the same slight not quite herself but really you could be imagining it behavior..

"sighs" Am I crazy? Has anyone noticed anything at all like this before with fly strikes? Or any sorts of underlying health problems? Arghh.....and may you never even have one in the first place.

Ivermectim spray for fly strike

350ml water in spray bottle. .125 ml 1% injectable ivermectin. Shake well before use. Spray fly strike area including wounds. They should be dead within 1-2 hours and falling off. Pick off remaining maggot corpses. Probably should not use on Dutch, BEW, and VM/VC rabbits.

I have noticed fly's are more attracted to sick animals than well ones-- but- it is often a mystery to me also... i have often smelled a sick animal before I saw any other signs.. I have a very sensitive sense of smell ...

I often use injectable ivermectin SQ , at 1 ml / 6 to 9 lb rabbit at the beginning of bot-fly season [just after I start seeing bot flies near the rabbit cages] , this "usually" prevents infection for the rest of the year... This might work for you also...

I might try that with this doe just to help keep them off her. How long does ivermectin stay in the system? I can handle dealing with the strikes themselves although they are nasty in every way. I am more concerned about the strikes indicating sick rabbits and making sure I don't let them suffer, and overall herd health is top priority. But I am not ready to let this doe go so I will give that a shot lol no pun intended Thanks

imajpm wrote:I might try that with this doe just to help keep them off her. How long does ivermectin stay in the system? I can handle dealing with the strikes themselves although they are nasty in every way. I am more concerned about the strikes indicating sick rabbits and making sure I don't let them suffer, and overall herd health is top priority. But I am not ready to let this doe go so I will give that a shot lol no pun intended Thanks

Ivermectin stays in the system somewhere between one and two months .. If you live in an area with long summers you may have to treat a few times... When I lived in Florida, I treated adult breedstock every other month from May to October...

Bacteria and yeast definitely have a smell when opportunistic infections overwhelm weakened immune systems and often different body tissue will have a smell as well. It could be the disease directly or it could be other things that result from it but it is often detectable to non-human critters. Animals are far more sensitive to such smells. Insects often base their entire lives and finding of food sources around very tiny differences in gases. While co2 is the most obvious thing given off by living animals and used to attract insects to traps studies have found mosquitos and other pests can detect many other gases. They are more likely to bite certain people based on various factors that result in a change in the exact gas combination and therefore odor equivalent being given off. Insects are likely superior to even dogs in their ability to "smell" disease.

Usually ivermectin is only considered effective for pests for 1-2weeks in the body before the concentration is too low to kill many external pests. Mites require every 7-10 day treatments or the ones that hatch after 5-7days will survive the ivermectin to reinfest the animal. Similar with most other things. For internal parasites you often use it every 2months in livestock but that's just to keep getting rid of what has managed to establish since the last dose rather than to keep killing everything they are exposed to for that month. You are treating the past month of exposure rather than the future month. Same with heartworm in dogs when using ivermectin. Despite using it monthly you are not stopping them getting infected. You are hopefully killing off all the worms while still young that have built up since your treatment the month before. Ivermectin tends to make a very poor preventative for that reason unless you know exposure will only cover certain weeks. Generally it's used when a low pest population in the body is not an issue between doses or every 7-10days for ~3 doses when an occasional acute infestation happens. Not so great if you want to stop an external parasite from doing very quick damage any possible day over many months.

If I wanted constant protection in similar form I'd look at one of the avermectins that last longer but they are expensive (revolution-selamectin) or have a much lower safety margin leading to accidental toxic doses in even large animals (moxidectin). I have gotten revolution without a vet from petshed.com and used it on various small animals but ongoing it gets costly. It's just useful when the mice try to move in during the fall and we have 2 months of rat mites trying to take over. I have a lot less pest mice venturing indoors since I got snakes.

Otherwise I'd just use a fly spray meant to be applied frequently and spray the surrounding structures or even the rabbits prone to problems. I sprayed cattle and horse fly repellent around the rabbits several times and even on a box of kits after a litter mate died and attracted flies with no adverse reactions. I never checked what chemicals we had for the various brands though. When we had chickens die to buffalo gnats I found essential oil based insect repellents soaked into the door frames of the coops actually worked awesome for some time past the 2 months their breeding season lasts. Fly traps and large stable strips for fly tape can be a good idea for your general house or horse fly type species. Might not do anything about bot flies. Those never got numerous enough to cause us real issues with any livestock and we mostly ignored them.

Green bottle fly is what they are. I do have the fly tapes up, and fly bags but they are empty,except the tapes, those are catching some gnat things not flies lol. I don't have a detectable fly problem but obviously they are stopping by. Frustrating to see no flies anywhere until you find a rabbit being eaten alive...

I had not considered that sprays might work on the rabbit itself. I did look at ivermectin but that doe is bred and there is a 2017 study out,on ivermection and fertility issues in rabbits, and so losing the litter isn't an option. Granted, they used a TON of ivermectin on the pregnant study does, daily doses, and weekly doses on the bucks so it may or may not be fine but that's her last litter so I'd rather not chance it. For now I am doing twice daily checks for eggs which offends her greatly lol.

Ok great thanks to both of you. Our fly season should be over in about 2-3 weeks but once I digest all this I think I'll be able to be more proactive than reactive.

imajpm wrote:Green bottle fly is what they are. I do have the fly tapes up, and fly bags but they are empty,except the tapes, those are catching some gnat things not flies lol. I don't have a detectable fly problem but obviously they are stopping by. Frustrating to see no flies anywhere until you find a rabbit being eaten alive...I had not considered that sprays might work on the rabbit itself. I did look at ivermectin but that doe is bred and there is a 2017 study out,on ivermection and fertility issues in rabbits, and so losing the litter isn't an option. Granted, they used a TON of ivermectin on the pregnant study does, daily doses, and weekly doses on the bucks so it may or may not be fine but that's her last litter so I'd rather not chance it. For now I am doing twice daily checks for eggs which offends her greatly lol.

Ok great thanks to both of you. Our fly season should be over in about 2-3 weeks but once I digest all this I think I'll be able to be more proactive than reactive.

I have read that ivermectin can cause "breeding problems" and also compromise a doe's pregnancy . However,- I have not noticed any trouble in my rabbits- And.. as Akane mentioned above, my theory is .. that ivermectin will kill any immature bot fly larva, round worms, or "bugs" present in the rabbits. I suppose sensitivity to drugs or chemicals could/ would follow genetic lines... So, my experience with ivermectin does not indicate that it is safe for all rabbits. I do try to avoid giving any kind of drug, herb, or even handling does, in the first 2 weeks of pregnancy.. I routinely offer wormwood [cut and sifted] to all rabbits each fall, after the first heavy frost. I never give it to a pregnant doe , but instead wait until her litter is a couple of weeks old..

Although I have not had "fly strike" issues more than once or twice in almost 60 years of raising rabbits..-- I have had bot fly problems in rabbits from time to time -the Florida swamp I lived in was bad, as was western Montana, and the mountains of southern Utah... here in N E Tennessee, I have not seen any yet... Sometimes I would see the squirrels , or cottontails going crazy, and know we had bot fly in the area long before I saw any flies around the rabbits.

michaels4gardens wrote:I have read that ivermectin can cause "breeding problems" and also compromise a doe's pregnancy . However,- I have not noticed any trouble in my rabbits- And.. as Akane mentioned above, my theory is .. that ivermectin will kill any immature bot fly larva, round worms, or "bugs" present in the rabbits. I suppose sensitivity to drugs or chemicals could/ would follow genetic lines...

Yeah German Angoras are on the ivermectin sensitive list. I am not entirely sure why, as it is very widely used in this breed. There are known vienna carrying lines though. There are also a LOT of breeders who use it for maintenance. There are also fertility issues for some breeders. If there is any correlation between the two I don't know. It seems like it is not something any of them pay much attention to. It's used after every shearing (every 90 days), before transport, and for actual legitimate treatments. Too often imo. I have used it once for early ear mites, but then I just switched to olive oil with the same result, then I used it for a wooler buck who presented with EC based on some internet chatter about it being miraculous in addition to fenbendazole. I saw nothing miraculous though. And then the maggot killing spray. I just don't do maintenance medicating on rabbits who have no problems. Keeping strong healthy rabbits is pretty important in this breed due to it's limited genetic pool but that isn't something very many breeders seem concerned about either.

I've never had a problem using ivermectin prior to breeding or in pregnant animals. Rabbit or otherwise. I actually prefer to dose a pregnant or nursing doe to get rid of an acute problem so I don't have to risk measuring it out for very young and small offspring. I find a topical dose especially seems to be just enough to also get any not weaned offspring without side effects or having to use other options on them. I know a few breeds are too sensitive to use it at all but aside from those cases I haven't seen a problem with a typical dose and usage. However, as I explained I don't think typical usage would work as a preventative in this case. You'd have to go beyond the usual dosing schedules of no more than once a month, usually every other month, or 3-4 doses in a row and then not again until another pest infestation for acute problems. In that case you quite likely could see problems or at minimum end up with resistance parasites. Another reason I pay the cost of revolution is that so few have been willing to for even dogs or cats that less pests have gained resistance to it. With it killing heartworms it is also restricted to veterinary dispensing in the US unless purchased from overseas companies so fewer people go through the effort to get it for small animals or livestock. It makes it worth it when I have a reason to use it.

With the fly population not being on your property repellents are probably one of the best ways to go. Just make the place and your rabbits unappealing. Various plants work as insect repellents including some colorful flowers so many will plant strips alongside buildings or cage blocks both for looks and as natural pest insect repellent. Spraying down any wood structures whether it's a building frame or cage supports with chemicals and essential oils can sometimes be effective for months. If you have power a fan and/or bug zapper are good ideas. Insects dislike air movement. The bugger zapper was just plain satisfying when I lived next to land set aside for wildlife and has horrid flying pest problems. I have mini zappers plugged into my wall outlets now to get stray indoor pests. They do have battery powered camping options for all those things as well. Several week or month long repellent releasing devices that are sometimes refillable and sometimes have battery driven fans to disperse it, battery powdered fans, and battery powdered bug zappers. It just may not be the most cost effective or convenient to keep them charged in some cases.

Lol the zappers. I WANT! That sounds rather like fun. Looks like we are diving headfirst into fall without much of a transition so the fly troubles should be over for this year shortly. Even the wasps have lost most of their population in just days. Usually they are all out of the nests/hives and raging around stinging people but we seem to be skipping that phase yay!